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posted by martyb on Wednesday December 27 2017, @02:10AM   Printer-friendly
from the whatever-happened-to-the-Even-Seasons? dept.

A central conceit of George R.R. Martin's A Song of Ice and Fire books (and the popular HBO series Game of Thrones based on them) is that the seasons of the planet where they take place are not as predictable as the Earth's annual cycle. Somehow the phrase "winter is coming" wouldn't seem as foreboding if you could reply, "Yes, that usually happens in December through February."

But how could a planet have unruly seasons? Earth's seasons are due to the tilt of its axis. During one part of Earth's orbit, the Northern Hemisphere is tilted away from the Sun, with the resulting indirect sunlight spread thin over the surface of the hemisphere, causing winter. On the opposite side of its orbit, summer comes as this hemisphere is tilted toward direct sunlight. There isn't much room in such clockwork for randomness.

Well, if you've ever wanted to debate fan theories, here's an excellent new resource for you to draw from: a real climate model simulation of Westeros and Essos.

Source: Ars Technica


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  • (Score: 3, Interesting) by zocalo on Wednesday December 27 2017, @10:46AM

    by zocalo (302) on Wednesday December 27 2017, @10:46AM (#614680)
    Other than portentious sunrises and sunsets, how many works of fiction set on Earth can you name where the characters have a lengthy discussion about the typical size and colour of the sun, except when it's some end-of-world style plot point? If you're looking to astrophysics for an retconned answer that doesn't get into complex orbital mechanics, then you might want to start with the idea that Planetos might be orbiting a variable star [wikipedia.org] instead though, most likely a long-period variable [wikipedia.org]. Like in the OP's suggestion, long period stars *do* tend to be red giants or similar but, as noted, the books don't specifically state the normal size or colour of Planetos' star as viewed by the inhabitants, and the show obviously uses our sun in shots for convenience - even so; depending on the energy output the Goldilocks zone could be much further out and result in the star appearing a similar size to our own in the sky.

    That allows for the irregular frequency and duration of summers and winters within human timescales since they are not really defined in the books as seasons per se, but more by temperature and day length - even after winter officially arrives, there are still plans being laid for setting aside food stocks from harvests. Nor does it preclude that there could also be more traditional seasons from an ellipitical orbit going on as well. The biggest problem GRRM sets is the change in day length, and that during the Long Night daytime didn't come at all, but there's a human precedent for that too; the tradition in Islam is that the moon be physically observed to determine the start of Hajj - if it's cloudly it doesn't count and Hajj gets delayed. Perhaps some combination of a similar practice applied to extended periods without sighting the star, a physically dimmer star reducing light levels considerably, and inclement winter weather making clear skies less likely are used on Planetos? A huge stretch to be sure, but again, I don't recall GRRM writing anything that specifically rules it out.

    That's still not perfect though - glacial periods tend to mean clearer skies because the cold temperatures draw moisture out of the air as precipitation, but prevent it returning as it gets locked up in ice, and there's less exposed sea water to replenish the stocks. I think that's the point we needed another round of beers though, so I don't recall working out an answer to that one beyond "well, maybe it's all just fucking magic after all - what are you drinking?" :)
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